Nuclear calculations

Dr. Hafemeister One exciting Mossbauer experiment was done at MIT by Grodzens and Cohen and co-workers. They tried to obtain the value of AR/R between members of a rotational band. It was extremely exciting because supposedly the wave functions in these rotation nuclei are well understood, and nuclear calculations are feasible. There are few such parameters one can measure in nuclear physics quite as nicely. 

A breakthrough was achieved a few years ago when it was realized that an anal dic calculation of the deuterium recoil, structure and polarizability corrections is possible in the zero range approximation [76, 77]. An analytic result for the difference in (12.29), obtained as a result of a nice calculation in [77], is numerically equal 44 kHz, and within the accuracy of the zero range approximation perfectly explains the difference between the experimental result and the sum of the nonrecoil corrections. More accurate calculations of the nuclear effects in the deuterium hyperfine structure beyond the zero range approximation are feasible, and the theory of recoil and nuclear corrections was later improved in a number of papers [78, 79, 80, 81, 82]. Comparison of the results of these works with the experimental data on the deuterium hyperfine splitting may be used as a test of the deuteron models and state of the art of the nuclear calculations. 

K. Rutz, M. Bender, T. Biirvenich, T. Schilling, P.-G. Reinhard, J. Maruhn, W. Greiner, Superheavy nuclei in selfconsistent nuclear calculations , Preprint (1996), Institut fiir Thcoretische Physik, JWG Uni-vcrsitat, Frankfurt a M, to be published. 

A core management code system has been developed to predict the core parameters for operation and refueling plans within the design limitations. The nuclear calculation is based on diffusion theory and corrected with a bias method. Results from core physics tests and Post Irradiation Examinations (PIE) have been used to confirm the accuracy of these predictions. These verifications are also important to conduct various irradiation tests accurately. This section describes the method and verification for core and fuel management used with the JOYO MK-II core. 

HICKS, D., Nuclear Calculation Methods for Light Water Moderated Lattices, AEEW-R64 (1961). 

The results of Oils analysis indicate that use of Grundl and Fabry fission spectra gives better results except for the enriched uranium reactivity coefficients. Because the Grundl and Fabry fission spectrum of V has been verified by McElroy, the use of this fission spectra for the nuclear calculations may be more appropriate. 

Nuclear calculations are based on nuclear data selected from the best current sources of information fhroughout the nuclear industry and on mathematical computer codes developed by General Electric for fhe BWR. 

The Aircraft Reactor Experiment, a 2.5-MW(th) reactor, operated in the 1950s with a NaF/ZrF4molten salt, while the Molten Salt Reactor Experiment, an 8-MW(th) reactor, operated in the 1960s with a EiF/BeF2 molten salt. In these reactors, the fuel was dissolved in the salt whereas the AHTR uses solid fuel with a clean molten salt. Detailed studies will be required to determine the preferred composition of the fluoride salt. All of the candidate fluoride salts have somewhat similar properties. Preliminary nuclear calculations used Ei2BeF4 because its properties are well known. 

A special programme of reactor physics experiments is in progress with the objective of improving the accuracy of nuclear calculations for natural uranium SGHWRs by providing calibration data. 

Rutz, K., Bender, M., Biirvenich, T., Schilling, T., Reinhard, P.-G., Maruhn, J.A., Greiner, W. Superheavy nuclei in self-consistent nuclear calculations. Phys. Rev. C56, 238-243... 

From the nuclear calculations, the components of the temperature coefficient were estimated, as follows ... 

The fuel cost items which vary with thc.se two parameters are (1) bismuth iiiM iiiiiiy, (2) fuel inventory, (3) fuel burnup, (4) thorium amortization, thorium burnup, and ((>) chemical processing. Nuclear calculations spei ilietl the fuel concentrations for both core. and blanket and breeding ratios, These I alues were then used to determine the chemical processing l yclc for the blanket and the pertinent costs. 

Nuclear calculations. The values of the parameters investigated were... 

Results of Nuclear Calculations for Various Power Splits... 

Ba,si,n of nuclear calculations. To obtain comparative results, the following specifications were a.s.sumed for all cases ... 

Results of nuclear calculations. The results of the parametric study are summarized in Table 24-6 for all cases. The criti< al concentrations and conversion ratios for the cases using thorium as the fertile material are graphed in Figs. 24-21 through 24-25. 

The Oka-Koshizuka heat transfer correlation [7] and Watts-Chou correlation [25] are used to evaluate the cladding surface temperature for upward and downward flow regions, respectively, which is consistent with those in thermal-hydraulic coupled nuclear calculations. Heat transfer improvement by the grid spacer is not considered for conservatism. 

The peak fuel rod is defined as a fuel rod having the peak linear heat rate within an assembly, and it is used to evaluate the MOST within an assembly. The average channel is represented by the average linear heat rate over a fuel assembly, which is used for evaluating the average coolant density distribution to be utilized in the nuclear calculations. 

In order to obtain all necessary information about the core, part of which has been described above, a large number of nuclear and thermo-hydraulic as well as dynamic calculations had to be performed. To avoid excessive engineering costs and because of numerical difficulties certain simplifications in the calculational model had to be made in this regard proper treatment of the actual three-dimensional very heterogeneous geometry of the core posed a problem. Therefore the nuclear calculations were divided into two classes ... 

These in turn are used in the next nuclear calculation of the power distribution. Iterations between the thermohydraulic and nuclear parts are continued until satisfactory convergence of the nuclear eigenvalue is achieved. 

Theoretical and measured reactivity values are compared in Table VII, which lists only those measurements that were most important for the testing of the nuclear calculations and that allow a direct comparison without additional assumptions. 

---